(1) Field of the Invention
This invention relates to an improvement in a tractor transmission.
(2) Description of the Prior Art
Unlike a passenger car, a tractor requires a transmission providing a multipstep change speed at great reduction ratios in order to carry out varied operations.
There is a known tractor transmission which includes a backward and forward switching mechanism or so-called shuttle transmission mounted forwardly of a primary change speed mechanism to suit, for example, a loading and unloading operation which involves a frequent repetition of backward and forward movements. Such a transmission has a disadvantage of having to change a wheelbase when, for example, a secondary change speed mechanism mounted rearwardly of the primary change speed mechanism and providing two speeds is modified or replaced with a new mechanism to provide three speeds.
Where a high speed and low speed switching mechanism is mounted forwardly of the primary change speed mechanism, it is sufficient that the secondary change speed mechanism provides two forward speeds and one backward speed. But in this instance the primary change speed mechanism must incorporate the backward and forward switching mechanism, which results in complicated construction and necessitates a change of the wheelbase.